【Spring】注入方法

添加maven依赖：

　　 <!-- spring基础包spring-core -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-core</artifactId>
      <version>5.2.8.RELEASE</version>
    </dependency>
    <!-- spring基础包spring-beans -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-beans</artifactId>
      <version>5.2.8.RELEASE</version>
    </dependency>
    <!-- spring基础包spring-context -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>5.2.8.RELEASE</version>
    </dependency>
    <!-- spring基础包spring-expression -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-expression</artifactId>
      <version>5.2.8.RELEASE</version>
    </dependency>
    <!-- spring依赖包 -->
    <dependency>
      <groupId>commons-logging</groupId>
      <artifactId>commons-logging</artifactId>
      <version>1.2</version>
    </dependency>

一、setter注入和构造方法注入 

在resources文件夹下创建配置文件applicationContext.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd">
    <!-- 将类配置到容器当中，让容器创建实例 -->
    <!-- setter注入 -->
    <bean id="hello" class="com.xiaobiti.HelloSpring">
        <!-- 给属性赋值 -->
        <property name="name" value="南宁第一深情"/>
    </bean>
    <!-- 构造方法注入 -->
    <bean id="User" class="com.xiaobiti.User">
        <constructor-arg name="id" value="1"/>
        <constructor-arg name="username" value="jojo"/>
        <constructor-arg name="password" value="1234"/>
    </bean>
</beans>

HelloSpring.java:

package com.xiaobiti;

public class HelloSpring {
    private String name;

    public void setName(String name) {
        this.name = name;
    }

    public void show(){
        System.out.println(name+",我在南宁很想你");
    }

}

测试类代码:

package com.xiaobiti;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestHelloSpring {
    public static void main(String[] args) {
        //加载核心配置文件
        ApplicationContext  applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        HelloSpring helloSpring = (HelloSpring) applicationContext.getBean("hello");
        helloSpring.show();
    }
}

运行结果：

上面已经展示的是setter方法注入，构造方法注入如下

User.java:

package com.xiaobiti;

public class User {
    private int id;
    private String username;
    private String password;

    public User(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

测试类代码：

　　public static void main(String[] args) {
        //加载核心配置文件
        ApplicationContext  applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        User u = (User) applicationContext.getBean("User");
        System.out.println(u.toString());
    }

运行结果：

二、依赖注入

创建一下文件结构：

包名.dao.UserDao.Java:

package com.xiaobiti.dao;

public interface UserDao {
    public boolean login(String username,String password);
}

包名.dao.impl.UserDaoImpl.java:

package com.xiaobiti.dao.impl;

import com.xiaobiti.dao.UserDao;

public class UserDaoImpl implements UserDao {
    @Override
    public boolean login(String username, String password) {
        if (username.equals("admin") && password.equals("1234")){
            return true;
        }
        return false;
    }
}

包名.service.UserService.java:

package com.xiaobiti.service;

public interface UserService {
    public boolean login(String username,String password);
}

包名.service.impl.UserServiceImpl.java:

package com.xiaobiti.service.impl;

import com.xiaobiti.dao.UserDao;
import com.xiaobiti.service.UserService;

public class UserServiceImpl implements UserService {
    private UserDao userDao;
    //setter方式注入
    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

    @Override
    public boolean login(String username, String password) {
        return userDao.login(username,password);
    }
}

applicationContext.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd">
    <!-- 将类配置到容器当中，让容器创建实例 -->
    <!-- 注入dao -->
    <bean id="userDao" class="com.xiaobiti.dao.impl.UserDaoImpl"/>
    <!-- 注入service -->
    <bean id="userService" class="com.xiaobiti.service.impl.UserServiceImpl">
        <property name="userDao" ref="userDao"/><!-- ref填入已经注入的userDao，对应上面bean中id=“userDao” ，setter注入方法-->
    </bean>
</beans>

测试类代码：

public static void main(String[] args) {
        //加载核心配置文件
        ApplicationContext  applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService userService = (UserService) applicationContext.getBean("userService");
        boolean flag = userService.login("admin","1234");
        if (flag){
            System.out.println("登录成功");
        }else{
            System.out.println("登录失败");
        }
    }